Union bargainers said they proposed paying a share of employee pension costs - they now make no contribution - in exchange for a pay increase, and extending the number of years needed to qualify for retiree medical benefits. BART officials said they proposed a comprehensive package of raises, pension contributions and health care costs.

Despite the small steps toward a potential agreement, union officials issued a voluntary 72-hour strike notification late Thursday night, advising commuters to prepare for a strike when the contract expires at 11:59 p.m. Sunday. Union officials have said employees will continue to work until BART's last scheduled trains reach the end of the line - about 1:30 a.m. Monday.

Governor's possible role

Then, if no agreement has been reached or no significant progress has been made, they'll hit the picket lines. Gov. Jerry Brown could stop a strike - temporarily - by ordering a 60-day cooling-off period. BART officials, who would rather endure a strike in the less-busy summer months, have asked him not to issue such an order. Amalgamated Transit Union has requested the cooling-off period.

Evan Westrup, a spokesman for the governor's office, said the requests had been received but that he could not comment on when or how the governor might act. In past BART labor disputes where cooling-off periods were issued, they generally only delayed the conflict for two months rather than leading to resolution.

Representatives from the two unions, BART and two state mediators were meeting through Friday night, with similar sessions planned for Saturday and Sunday.

Rick Rice, a BART labor spokesman, said much of Friday was spent waiting for the unions to respond to the transit agency's Thursday proposal.

"It's going slowly," Rice said.

Wages, safety at issue

Union officials said they have been waiting for BART's response to their latest proposal.

"We still want to avert a strike," said Josie Mooney, a chief negotiator for SEIU. "But if I were a betting woman, and I'm not, I would say it's extremely likely there will be a strike."

The unions, which represent about 2,300 train operators, station agents, mechanics, maintenance workers and professional staff, have proposed a 23.2 percent raise over three years and asked for safety improvements including staffing, lighting and opening restrooms. BART has proposed a 1 percent raise for each of four years and wants workers to contribute to their pensions and to increase their $92 monthly health insurance co-pays.

A typical station agent or train operator makes in the low to mid-$60,000 range each year and, according to BART, also collects an average of $11,000 for overtime work.

While negotiations crept forward Friday, Bay Area transportation officials urged people to plan for what promises to be a glacial commute if there's a strike Monday. They're encouraging workers to do their jobs at home or drive during off hours, and to carpool. BART station parking lots will be open - and free - as locations for casual carpools if there's a strike.

Limited shuttle buses

BART is also planning to operate very limited charter bus shuttles between the West Oakland and Embarcadero stations, and AC Transit plans to boost service on existing Transbay routes and run shuttles between downtown Oakland and the temporary Transbay Terminal. Those plans, however, could be affected by an AC Transit labor dispute. Commuters can also take ferries between Oakland, Alameda, Vallejo and San Francisco.

Caltrans plans to put on extra traffic engineers and toll collectors, and extra Freeway Service Patrol tow trucks will be on the highways to help keep traffic from completely bogging down.

"It's not going to be a lot of fun for anyone," said Bob Haus, a Caltrans spokesman.

Commute options in event of strike

Regional transit leaders are warning commuters to plan ahead for a strike, and 511.org provides drive-time data and transit links. Here are some transit options:

East Bay

-- AC Transit is expected to run a shuttle during peak hours between the 20th Street and Broadway transit center in downtown Oakland and the Transbay Terminal in San Francisco with buses running about every three to five minutes. BART plans to run limited charter bus service between its West Oakland and Embarcadero stations.

-- San Francisco Bay Ferry is expected to enhance service with extra boats from Oakland, Alameda and Vallejo. Both SolTrans from Solano County and WestCat from West Contra Costa County plan to increase their service in to San Francisco.

San Francisco

-- Muni plans to prioritize service on the 14-Mission and 49-Van Ness corridors.

North Bay

-- Golden Gate Larkspur Ferry does not have the additional capacity for parking or passengers, unless commuters are traveling during off-peak hours.

-- Golden Gate Transit Bus Service will still provide daily service, from outside El Cerrito Del Norte and Richmond BART stations, on Golden Gate Transit Route 40/42, no added service, regular schedules with available passenger capacity. Connect to other Golden Gate Transit bus service to and from San Francisco at the San Rafael Transit Center.

South Bay

-- Sam Trans plans to run a free shuttle between the Colma and Daly City BART stations and Mission Street near the Daly City-San Francisco border where riders can connect to Muni. Muni also plans to boost service, especially along the Mission Street corridor.

Driving

-- Drivers are encouraged to curb their travel during peak commute hours. Carpool lanes are expected to stay open all day.

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